# RE: Reversible computing

Assuming neurons aren't able to tap into QM stuff because of
decoherence, it seems odd that consciousness is performed with an
irreversible computation whilst the universe uses a reversible
computation.

- David

-----Original Message-----
From: Russell Standish [mailto:[EMAIL PROTECTED]
Sent: Thursday, 13 November 2003 9:59 AM
To: David Barrett-Lennard
Subject: Re: Reversible computing

I think the answer to your question is yes (assuming I understand you
correctly). Information and probability are closely linked (through
algorithmic information theory - AIT for those acronym
lists). Schroedinger's equation is known to conserve probability
(basically |\psi(t)| is a constant - usually set to 1 - under
evolution by Schroedinger's equation (|.| here means Hilbert spoace
norm, not
absolute value)). This conservation of probability turns out to be
equivalent to unitarity of the Hamiltonian operator, which guess what,
means energy is conserved.

Unitary evolution is a reversible computation, which is why quantum
computations are reversible.

Cheers

David Barrett-Lennard wrote:
>
> I have been wondering whether there is something significant in the
fact
> that our laws of physics are mostly time symmetric, and we have a law
of
> conservation of mass/energy.  Does this suggest that our universe is
> associated with a reversible (and information preserving) computation?

>
> - David

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A/Prof Russell Standish                  Director
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UNSW SYDNEY 2052                         Fax   9385 6965, 0425 253119
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